The invention relates to a method of controlling water condensation in the pores of a near wellbore region of a permeable formation.
Condensation of hydrocarbons in gas-condensate reservoirs is well known in the industry (see e.g. SPE paper 30767 published by Exxon, and SPE papers 30766 and 36714 published by Shell). The condensation of the hydrocarbons causes a liquid zone to be formed in the reservoir close to the well bore. This liquid is understood as acting to hamper gas flow, reducing the productivity of the well. It is assumed that this liquid drop out already occurs iso-thermally. SPE paper 94215 discusses drying of a water block, assuming a negligible effect of Joule-Thomson. In line with other literature discussing water blocks in gas reservoirs, it is assumed that the water block is formed during drilling, by fluid invasion from the drill hole into the reservoir.
Well impairment is an important problem in oil and gas field engineering. It causes that more wells need to be drilled to achieve a certain field production rate. To reduce impairment, it may require additional investment into fracturing jobs and/or underbalanced drilling. Increased investment cost may even prevent development of fields in an area believed to suffer frequently of flow impaired wells.
The method according to the preamble of claim 1 is known from SPE paper 100182 “Wettability alteration for Water Block Prevention in High-Temperature Gas Wells” presented by M. K. R. Panga et al at the SPE Europec/AEGA Annual Conference held in Vienna from 12 to 15 Jun. 2006. This paper describes the development of a chemical system for water block prevention in gas/condensate wells. The chemical system alters the formation wettability thereby decreasing the capillary forces and enhancing the clean up of trapped water at low drawdown pressures. Placement of such a chemical system is a complex procedure and the injected chemicals may be washed away. The SPE paper only teaches how to promote flux of water that is already present in the pores of the formation and not that the natural gas may contain water vapor which may condense in the formation in the vicinity of the well and how to inhibit or promote condensation of water vapour in the pores in the formation in the vicinity of the wellbore.
It is an object of the present invention to provide a method for controlling wet gas production such that development of a water bank resulting from condensation of water in the pores of a near wellbore region of a permeable formation is inhibited or promoted.